Method of coloring coal



Sept. 13, 1938. G. BARsKY r-:r AL l 2.129,902

METHOD oF coLoRING COAL Filed June/13, 1935 WASTE' Co/M 7l'0 C14/75 INVENTORS BYS Y ATTORNEY.

Patented sept. 13, 193s METHOD or coLoRlNG. coAL George Barsky, New York, N. Y., and Waldemar C. Hansen, Westfield, N. J., assignors to American Cyanamid Company, New York, N. Y., a corporation of Maine Application June 1s, 1935, serial No. 26,400

4 claims. `(c1. 44-s) UNITED .STATES PATENT OFFICE to overcome the above defects and to secure colored coal where the color is adherent, cannot be readily rubbed off, is resistant to weathering, which will present a reasonably uniform color or in which, if the color is not uniform, the variations thereof will produce a uniform objective effect.

To this end, the invention contemplates contacting coal with either an alkali or alkaline earth ferricyanide and particularly calcium ferricyanide, and a' ferric salt, both in solution form,

either as a combined solution or as a consecutive treatment with the individual solutions. The invention further includes Washing the coal prior to the coloring treatment in order to remove objectionable material and in also washing the colored material subsequent to the treatment in order to remove excess reactants, reaction products, dust, or all of these. The invention further consists in maintaining the particular solutions specified out of contact with metallic surfaces in order to maintain optimum reaction conditions when such solutions reach the coal or during their period of contact with the coal.

The invention further consists in the novel combinations of steps and" proportions of ingredients more fully hereinafter described.

The drawing illustrates a diagrammatic flow sheet in a typical treatment.

The coal should first be Washed to eliminate' objectionable material adhering thereto. This may be dust, slime, or mine Water. Such water is usually objectionable because of its content of sulfates. Experience has determined that unless these objectionable materials are removed from the surface of coal, they tend to either unduly decompose the coloring solution or they prevent the coloring 'solution from properly adhering to the coal or modify thefcolor to a detrimental ex tent. The thus Washed coal may then be passed to any desired type of tumbling equipment, that is, one in Which the coal may be made to turn .over and over to expose all of its surfaces to the coloring solution. In this apparatus, it is subjected to the coloring solution which may be either sprayed thereon or the solution may be in the form of a bath through which the coal passes.

Any alkali or alkaline earth ferricyanide will react with most ferrie salts to produce the desired blue color on coal. Calcium ferricyanide is preferred because of its cheapness, ease of manufacture, and also because a better quality of color and a more adherent coating appears to' be produced. Ferric nitrate, chloride and sulphate have been found to be satisfactory, although ferric chloride is to be preferred because of cheapness and ease of manufacture. A mixture of alkali and alkaline earth ferricyanide has been found to be particularly desirable with ferric chloride.

It is preferred to use theferricyanide as a solution containing an equivalent of 1% Ke3Fe(CN)s or .826% calcium ferricyanide and the ferric salt as a 2% ferric chloride solution.

It has been found desirable to maintain thesesolutions separate and not mix until just prior to contact with the coal to be colored.` As va consequence, they. may either be run separately into a mixing tank and thereafter the mixture sprayed or otherwise applied to the coal or they may be individually and consecutively applied to the coal, although the former method ls to be preferred.

The treating solutions have been found to be more stable if they are maintained out of contact with metal and this is particularly true if the ferricyanide and ferric salt solutions are mixed prior to application to the coal. y

For this reason, all surfaces coming in contact with such solutions should be either of rubber, wood, wood coated with non-metallic containing ims such as a synthetic drying oil resin, porcelain or glass, although the rst is to be preferred.

In commercial practice, it will be found advisable to apply the above solutions to the coal at the rate of approximately 21 pounds of each per ton of coal treated. Of course, this rate may vary withinlimits dependent upon the size of the solids treated, as the finer the particles, the more surface to be covered and consequently the greater the rate of solution feed must be. The excess solution may be drained from th exit end of the tumbling apparatus and through n.

any f'ust or any other loose particles which might have broken off from the coal lumps in the mechanical handling of the same. The thus washed colored coal may then pass to bins or cars for shipment.

It has been found that unless the c oal from the treating equipment is washed free of excess reactants or from reaction products, there is a tendency to dull the color, whereas after the washing operation, the surfaces remain bright and the color remains true even after long periods of time. Therefore, in the claims where the words subsequent washing are used it is intended to mean a Washing sufficient to free the treated coal from excess reactants or from reaction products as a deliberate step rather than some accidental treatment such as may occur by reason of a rain storm.

The very bright smooth surfaces of the coal appear to react more slowly than do the rather rough surfaces and, hence, there has been found to be some slight vcliierence in color between the smooth and rough surfaces. However, this difference ranges objectively from green to blue with the result that a violet blue elect is produced, even though upon close examination, small patches of varying color may appear.

While the invention has been shown and described with particular reference to certain embodinients, it obviously is to be construed broadly and limited only by the scope of the claims.

1. A method of coloring coal to secure a bright adherently colored surface substantially free from loose coal dust which comprises Washing the coal to remove coal dust from the surface thereof, and

immediately thereafter applying to the surface of thewashed coal a solution containing a ferricyanide of an alkali forming metal and a ferric salt, in a quantity less than that necessary to produce an equivalent color on coal from which the coal dust has not been removed, and immediately thereafter washing the thus treated coal to free the same from excess reactants, reaction products, or coal dust.

2. -A method of coloring coal which consists in applying to the surface thereof a solution containing a ferricyanide salt of an alkali forming metal and a ferric salt in the proportion of 21 pounds of a solution of a ferric salt equivalent to 2% ferric chloride, and 21 pounds of a solution of a ferricyanide equivalent to 1% K3Fe(CN) s. per ton of coal, and subsequently washing the thus colored coal to free the same from excess reactants or reaction products.

3. A method of coloring coal which consists in washing the same to remove objectionable material, applying to the surface of the Washed coal a solution containing a ferricyanide salt of an alkali forming metal and a ferrie salt in the proportion of 21 pounds of a ferric salt solution equivalent to 2% ferrie chloride and 21 pounds of a ferricyanide solution equivalent to 1% K3Fe(CN)5 per ton of coal, and subsequently washing the thus colored coal to free the same from excess reactants or reaction products.

4. The method of claim 2 in which the treating solution prior to and during contact with the coal is maintained out of contact with metallic surfaces.

GEORGE BARSKY. WALDEMAR C. HANSEN. 

